Mobile communication has been one of the most successful innovations in modern history. In recent years, the number of subscribers to mobile communication services has exceeded 5 billion and is growing fast. At the same time, new mobile communication technologies have been developed to satisfy the increasing needs and to provide more and better mobile communication applications and services. Some examples of such systems are cdma2000 1xEV-DO systems developed by 3GPP2, WCDMA, HSPA, and LTE systems developed by 3GPP, and mobile WiMAX systems developed by IEEE.